In current processing devices, to process a workpiece the operating spacing between a processing head and a workpiece is in most cases continually monitored and controlled with respect to a fixedly predetermined desired operating spacing. To this end, the processing head is moved during the processing operation towards the workpiece or away from the workpiece along at least one of the movement axes thereof.
For an optimum processing result on the workpiece, the smallest possible operating spacing of the processing head from the workpiece is often desired. This is particularly the case during thermal separation cutting operations or also in many welding applications. In such processing operations, sometimes costly process fluids (e.g., inert or active gases) are often used, the consumption of which increases as the operating spacing of the processing head from the workpieces to be processed increases.
In practice, the workpieces to be processed often have a surface which is not planar over the entire surface. For instance, in metal sheets there are occurrences of surface undulation which may originate, for example, from a previous production process of the metal sheets or also the arrangement thereof in a tool receiving member of the processing device used. Furthermore, the metal sheets may be thermally deformed by the processing operation. The metal sheets may also be arranged in an oblique manner with the surface thereof in the workpiece receiving member with respect to a movement axis of the processing head.
In industrial mass production, the processing head for processing the workpiece must be moved at high speed over the workpiece for reasons of economy. In this respect, the processing head during such applications cannot readily be moved with respect to the workpiece with a small operating spacing of, for example, 0.3 mm from the workpiece. The processing head, even with highly dynamically configured systems has a deviation of the actual position thereof from the desired position thereof in accordance with the respective movement speed, that is to say, a so-called trailing spacing, along the movement axes thereof. Taking into account the variable surface topography of the workpieces in the case of an excessively small desired operating spacing of the processing head from the workpiece, collisions of the processing head with the workpiece may occur. In addition to the resulting undesirable interruptions to the process, this may lead to damage of the processing head (for example, the focusing lens of a laser processing head) or the workpiece. This is disadvantageous for the processing result and the efficiency of the method.